It seems that there is controversy regarding oxygen humidification in literature.
Dear Fatemeh Khoshnavay fomani , below link will be helpful for you.
https://vapotherm.com/blog/the-need-for-airway-humidification-in-covid-19-patients/
Dear Fatemeh!
Please You look at link below:
Guideline for the management of COVID-19 patients during hospital admission in a non-intensive care setting
Article Guideline for the management of COVID-19 patients during hos...
Hypoxic respiratory failure (type 1)
Oxygen/O2
To date, no evidence of optimal oxygen treatment for COVID-19 patients is known, neither in terms of a method for administration nor for target saturation (SpO2).
Oxygen should be administered through a conventional bi-nasal cannula or a high-flow nasal cannula in patients with a need for a fraction of inspired oxygen (FiO2) 40% (equivalent to approx. 5 L/min on ordinary bi-nasal cannula), flow can be increased, still without humidification, to 6 to 15 L/min by using a high-flow nasal cannula, thus achieving a FiO2 of approximately 40 to 60%. For achieving higher FiO2, please consult the paragraph below on high-flow nasal cannula (HFNC).